The aggregation behavior of surfactants in aqueous media is a robust area of investigation. Various vesicle compositions, such as liposomes and the like, have been developed for many applications with particular emphasis on the design of such systems for delivery of active materials via a pharmaceutical or personal care product formulation. Long-standing needs in this field are to identify vesicle compositions that form and entrap actives easily, are stable under various chemical and mechanical stresses, and yet are able to deliver the actives in a controlled manner under desired conditions. To this end, many classes and types of surfactants have been investigated for their ability to form vesicles and thus entrap and deliver actives.
Vesicles derived from silicone surfactants, and more particularly silicone polyether surfactants, are of interest because of additional inherent benefits that this class of surfactants possesses vs other types. For example, silicone surfactants often have improved aesthetics in personal care formulations.
The aggregation behavior of certain silicone polyethers has been discussed along with their ability to form vesicles. For example, U.S. Pat. Nos. 5,364,633 and 5,411,744 by Hill teaches the self-assembly of certain silicone polyethers in aqueous media to form vesicles. PCT Application US2003/38455 by Lin teaches the entrapment of various oils in certain silicone polyether vesicles and their use in various personal care formulations.
While these references represent advancements in the art, a need still exists to create silicone vesicles having improved stability. For example, the silicone vesicles formed from the self-assembly procedures can lack durability. This lack of durability can limit the processing conditions they can be subject to in the formation of various finished products. Furthermore, such self-assembled silicone vesicles can lack the ability to provide sustained release of loaded actives over an extended period of time. Thus, a need exists for a process to prepare silicone vesicles having improved durability and the ability to release loaded actives over an extended period of time.
The present inventors have discovered that high molecular weight silicone polyethers (SPEs) form vesicle compositions in aqueous media. The vesicle compositions possess enhanced stability and are useful to prepare formulations for the delivery of personal, household, and healthcare active materials.